Search Results (1,083)

Postoperative respiratory failure (PRF) remains a pervasive clinical challenge that substantially contributes to perioperative morbidity, mortality, and prolonged ICU stay. Although conventional oxygen therapy is often sufficient, a significant subset of high-risk patients requires escalation to advanced non-invasive support to avoid reintubation and invasive mechanical ventilation. Evidence from recent randomized trials, including the 2025 RENOVATE and Goret et al. studies, indicates that both non-invasive ventilation (NIV) and high-flow nasal oxygen (HFNO) reduce postoperative pulmonary complications and reintubation in selected high-risk populations. While NIV is preferred for hypercapnic ventilatory failure and is commonly used in selected high-risk cardiac surgery patients, HFNO offers comparable outcomes in pure hypoxemic failure with the added benefits of superior patient tolerance and a lower incidence of interface-related complications. Effective PRF management necessitates an individualized, physiology-based approach. By implementing a phenotype-driven algorithm that aligns device mechanics with the dominant pathophysiology, such as atelectasis versus pump failure, clinicians can optimize patient outcomes while minimizing the specific risks associated with delayed intubation. Full article

Distributed recycling of high-density polyethylene (HDPE) into filament for use in material extrusion 3D printing has been proposed as part of a circular economy. There is a gap in the understanding of the potential for HDPE to release contaminants that are potentially hazardous to human health during reuse. Herein, HDPE from post-consumer packaging waste was sorted into food and non-food (NF) streams and virgin HDPE was taken as a benchmark material. All materials were extruded into filaments and recycled multiple times while monitoring emissions. In general, particle and organic chemical emissions decreased by 93 to 99% and 73 to 99%, respectively, with increased reprocessing cycle without appreciable decline in mechanical (Young’s modulus decreased by 5 to 16%), processability (melt flow index stable from 0.2 to 0.7 g/10 min for waste plastics), and thermal properties (crystallinity ranged from a 6% decrease to a 9% increase) of plastics. An exception was a sub-stream of NF plastic that had increased particle emissions (up to 3100%) with reprocessing cycle. Reductions in emissions during filament extrusion appeared to be more influenced by reprocessing cycle than by any specific process step (grinding, etc.). The progressive decline in emissions without appreciable loss of polymer integrity could be exploited to pre-condition HDPE to reduce potential hazardous emissions prior to extruding into filament. This work helps fill the knowledge gap on approaches to recycling plastics in distributed settings such as home-based businesses, which is critical for developing effective recommendations for controls to enable safe work practices such as the use of ventilation to minimize exposures. Full article

Patients with end-stage lung diseases awaiting lung transplant frequently experience severe hypoxemia, dyspnea, and functional limitations that may compromise survival and transplant eligibility. Optimizing noninvasive respiratory support during the waiting period is crucial to preserve oxygenation, maintain physical conditioning, and avoid escalation to invasive mechanical ventilation, which is associated with poorer transplant outcomes. High-flow nasal cannula therapy has emerged as an important noninvasive respiratory support modality capable of providing physiological and clinical benefits such as precise fractions of inspired oxygen, a low level of positive end-expiratory pressure, dead-space washout, and reduced work of breathing. This review summarizes the pathophysiology of hypoxemia in lung transplant candidates, the mechanisms of action of high-flow nasal cannulas, and the current clinical evidence supporting its use in this population during the pre-transplant period. Available evidence suggests that the use of high-flow nasal cannulas improves oxygenation, relieves dyspnea, enhances exercise tolerance, facilitates participation in pulmonary rehabilitation programs, and may reduce the need for endotracheal intubation, thereby improving the likelihood of survival to transplantation. The review also discusses patient selection, the practical implementation of high-flow nasal cannula therapy, and comparisons with other respiratory support modalities. Although the current evidence is largely observational and heterogenous, high flow appears to be a valuable supportive and bridging therapy for selected patients awaiting lung transplant. Future prospective studies are needed to define standardized protocols and evaluate transplant-specific outcomes. Full article

In fire emergency ventilation systems, EC (Electronically Commutated) internal-rotor axial fans are critical devices, but their high-speed operation generates aerodynamic noise often exceeding 90 dB (A). While struts are core structural components regulating flow field stability, their specific geometric impact on trailing-edge vortex shedding and noise generation mechanisms remains unclear. This study investigates three strut configurations: a hexagonal annular type, a hexagonal double-ring type, and a three-pronged type. A coupled numerical model was established using Large Eddy Simulation (LES) and the Ffowcs Williams and Hawkings (FW-H) acoustic analogy. The Q-criterion was employed to analyze vortical structures, with numerical predictions validated against experimental measurements in a semi-anechoic chamber. The results quantitatively demonstrate that optimizing the strut geometry significantly mitigates unsteady flow separation. The three-pronged strut (Model C) effectively dispersed high-velocity airflow, reducing the peak turbulent kinetic energy (TKE) at the inlet by 30% compared to the original design (Model a). Furthermore, Model C achieved a 6.7 dB reduction in the sound pressure level at the blade-passing frequency (BPF), alongside a 14.1% reduction in pressure pulsation amplitude near the blade tip. Structural optimization of struts enables synergistic control over turbulence distribution and pressure fluctuations. By disrupting the phase coherence of shed vortices, the optimized design fundamentally suppresses aerodynamic noise, advancing axial fan design toward precise quantitative aeroacoustic optimization. Full article

Emergent tracheal intubation in critically ill patients is a common, yet high-risk, intervention. It is frequently complicated by peri-intubation hypoxemia, hemodynamic instability, and metabolic derangements that increase the risk of arrhythmias, hypotension, cardiac arrest, and death. Because the highest-risk interval often occurs in the minutes surrounding induction, when apnea, derecruitment, and abrupt cardiopulmonary shifts converge, oxygenation failure frequently reflects a mismatch between preoxygenation strategy and the underlying physiology rather than inadequate oxygen delivery alone. This review proposes a phenotype-based approach to peri-intubation oxygenation and focuses on four high-risk phenotypes in whom standard preoxygenation strategies commonly fail: obesity, neuromuscular disease, right ventricular dysfunction or pulmonary hypertension, and post-operative respiratory failure with altered respiratory mechanics or airway anatomy. We summarize the key mechanisms that shorten safe apnea time, including reduced functional residual capacity, intrapulmonary shunt, elevated oxygen consumption, rapid derecruitment after induction, and impaired oxygenation–hemodynamics coupling. We then compare preoxygenation modalities as physiologic tools, including facemask oxygen, high-flow nasal cannula (HFNC), noninvasive ventilation (NIV), and controlled bag-mask ventilation (BMV), and integrate contemporary randomized trial evidence that informs bedside selection and combination of these approaches. Finally, we synthesize these concepts into a practical, physiology-informed framework to guide clinicians in choosing and troubleshooting preoxygenation strategies in high-risk patients undergoing emergent intubation. Full article

Objectives: To confirm the utility of barometric whole-body plethysmography (BWBP) as a non-invasive, clinical diagnostic test for brachycephalic obstructive airway syndrome (BOAS) in cats. Methods: Client-owned cats belonging to brachycephalic breeds were enrolled and classified into two clinical severity grades of upper airway obstruction (UAO). Brachycephalic cats with high-grade UAO severity (Brachy-H-UAO) represented those with clinically evident effects on clinical signs or physical examination findings, whereas brachycephalic cats with low-grade UAO severity (Brachy-L-UAO) represented those without clinically evident problems. A group of non-brachycephalic (NB) cats that were respiratory disease-free and with neither a history of cardiac or systemic diseases nor exposure to cigarette smoke was used as the control group. Cats were placed in the BWBP chamber, and breathing signals were obtained after an adaptation period in a quiet and silent environment. The ventilatory variables obtained were respiratory rate (RR; [bpm]), tidal and minute volume per kilogram bodyweight (MV/BW and TV/BW; [mL/kg]), inspiratory (Ti; [s]) and expiratory (Te; [s]) intervals, airway obstruction index enhanced pause (Penh), and peak inspiratory and expiratory flows per kilogram (PIF and PEF; [mL/s/kg]). Results: Forty-three client-owned cats (11 Brachy-H-UAO, 7 Brachy-L-UAO, and 25 NB) were included. Brachycephalic cats (Brachy-H-UAO: 311 mL/kg; Brachy-L-UAO: 253 mL/kg) showed significantly lower median MV/BW than NB cats (503 mL/kg) (p = 0.01). Brachy-H-UAO cats demonstrated significantly higher median PEF/PIF ratios (Brachy-H-UAO: 1.46, minimum–maximum 0.82–2.48; Brachy-L-UAO: 0.76, 0.52–1.11; NB: 0.73, 0.56–1.00) and Penh (Brachy-H-UAO: 2.37, minimum–maximum 0.57–23.82; Brachy-L-UAO: 0.57, 0.27–1.11; NB: 0.53, 0.21–0.68) than Brachy-L-UAO and NB cats (p < 0.001). No significant differences were observed among the three groups for RR, TV/BW, Ti, Te, or Te/Ti. Conclusions and Relevance: Cats affected by BOAS demonstrate impaired ventilatory function, with reduced minute ventilation and a distinctive flow pattern and parameters reflecting limited inspiratory flow and increased upper airway resistance. BWBP can serve as a useful tool to diagnose and characterize the severity of BOAS in cats. Full article

Background/Objectives: Myositis-associated interstitial lung disease (ILD) can occasionally present as acute respiratory distress syndrome (ARDS); however, clinical data on this presentation remain limited. This study aimed to describe the clinical characteristics and outcomes of patients with myositis-associated ILD presenting as ARDS. Methods: We conducted a single-center retrospective observational study of patients with myositis-associated ILD who were admitted to the intensive care unit (ICU) for acute hypoxemic respiratory failure. Results: Ten patients positive for myositis-specific antibodies met the new global ARDS definition. The median age was 62 years, and eight patients were male. Antibody profiles included anti-MDA-5 (n = 5), anti-synthetase antibodies (Jo-1 [n = 1], PL-7 [n = 2], EJ [n = 4]), and NXP-2 (n = 1). Fever and cutaneous manifestations were the most common extrapulmonary features. Chest computed tomography demonstrated diffuse alveolar damage patterns in six patients and organizing pneumonia patterns in four. At ICU admission, four patients required mechanical ventilation and six received high-flow nasal cannula, of whom four subsequently progressed to mechanical ventilation. Extracorporeal membrane oxygenation was implemented in three patients. All patients received high-dose corticosteroids, six underwent steroid pulse therapy, and four additionally received immunosuppressive agents. Six patients died during hospitalization. Conclusions: Myositis-associated ILD may present as ARDS and should be considered in patients with ARDS of unclear etiology. Careful physical examination and autoantibody testing may assist in recognizing this condition in the critical care setting. Full article

Modern underground hard coal mines encounter increasing natural hazards as mining depth increases, including, in particular, significant rises in both methane and thermal hazards. Thermal threats are common in Polish mines, especially in areas where the primary rock temperature exceeds 40 °C. To provide an energy source for cooling systems and reduce methane emissions from ventilation air, a system based on a catalytic reactor combined with an absorption chiller was developed. Field tests conducted at the experimental mine Barbara in Mikołów (Poland) indicate that a COP based on methane chemical energy can reach a level of 0.3–0.4. An application analysis was conducted based on the results of cross-sectional forecasts of climatic conditions (thermal conditions forecasts). The results indicate the potential for using this installation as a supporting component of mine cooling systems. An important factor that may limit the efficiency of the installation is the volume flow of the exhaust air stream. It is estimated that, in countries where, as in Poland, air temperature is the primary criterion for assessing thermal safety, the results of the analysis would be similar. Full article

Low-concentration methane emissions from landfills, manure management, wastewater treatment, and ventilation streams are difficult to mitigate using conventional capture and oxidation because of high air-to-fuel ratios, variable flows, and unfavorable economics. Methanotrophic bioreactors provide an aerobic biological route to oxidize methane at ambient conditions and, in selected cases, enable valorization into biomass and bioproducts. This review synthesizes methanotrophic reactor technologies for dilute methane, emphasizing the design and operational constraints that control performance. We classify systems into (i) fixed-film gas–solid configurations (biofilters, biocovers, biotrickling filters, and bioscrubbers), (ii) suspended-growth gas–liquid reactors (stirred tanks, bubble columns, and loop/airlift designs), (iii) membrane-based and intensified contactors that decouple methane and oxygen delivery and enhance mass transfer, and (iv) hybrid and in situ approaches for diffuse sources. This review presents key metrics and discusses how mass transfer, moisture and temperature control, nutrient supply, and microbial ecology interact to define achievable removal. We further summarize recent techno-economic and life-cycle studies to identify dominant cost drivers, particularly air handling and gas–liquid transfer, and the concentration regimes where biological oxidation is competitive with catalytic or thermal alternatives. Full article

Introduction: Severe traumatic brain injury (sTBI) frequently coexists with polytrauma and often necessitates damage control neurosurgery (DCNS), where rapid decompression and temporary stabilization take precedence over definitive reconstruction. Within this context, anesthetic management must balance cerebral protection with ongoing resuscitation, yet high-quality DCNS-specific evidence remains limited. Materials and Methods: A comprehensive search of PubMed, Scopus, and Google Scholar (2015–2025) was conducted using MeSH terms and keywords related to neurotrauma, anesthesia, intracranial pressure, and perioperative management. Studies were included if they examined anesthetic or hemodynamic strategies in severe TBI or DCNS and reported relevant clinical or physiologic outcomes. Results: Nineteen articles addressing perioperative strategies for optimizing DCNS outcomes were analyzed. Discussion: Preoperative care emphasizes hemodynamic stabilization and permissive hypertension, damage control resuscitation including massive transfusion protocols, optimization of cerebral perfusion pressure (CPP) and neuromonitoring, and the use of hyperosmolar therapy. Transexamic acid can be used in sTBI safely but with unclear improvement in outcomes. Intraoperatively, propofol-based total intravenous anesthesia is generally preferred over volatile agents due to favorable effects on intracranial pressure (ICP), cerebral blood flow (CBF), autoregulation, and emergence. While historically contraindicated, ketamine and etomidate are now increasingly used as hemodynamically protective induction agents. Analgesic and sedative strategies prioritize dexmedetomidine and carefully titrated opioids to minimize respiratory depression and reduce postoperative complications. CPP and ICP-directed management relies on individualized blood pressure targets, vasopressor selection, lung-protective ventilation, and strict temperature control. Conclusions: Emerging evidence has suggested the benefit of DCNS for patient survival. Overall, perioperative care is guided largely by physiology and extrapolation, highlighting the need for standardized protocols. Full article

Background: Accessory ostia (AOs) can notably alter maxillary sinus ventilation, yet configuration-specific effects remain unclear. This study quantified how AO location and orientation regulate sinus ventilation using in vitro measurements and numerical analyses. Methods: One patient-specific sinonasal geometry (control) was used to reconstruct five models with varying AO numbers, locations, and orientations (AO-F, AO-FC, AO-F30, AO-B, AO-FB). E-vapor was used as a visual tracer for sinus clearance under breath-hold and quiet breathing conditions. Complementary simulations characterized flow dynamics and sinus ventilation rates. Results: Both inhalation and AO presence accelerate e-vapor clearance for all conditions considered. The e-vapor clearance time in AO-FB decreases from 51 s under breath-hold to 29 s under quiet breathing (1 m/s). Configuration-wise, posterior AO ventilates the sinus faster than anterior AO, with dual anterior–posterior ostia (AO-FB) consistently performing the best. Among the three anterior AO, an uptilt AO ventilates the sinus faster than a parallel one, which is in turn faster than an AO located closer to the natural ostium (NO), i.e., AO-F30 > AO-F > AO-FC. CFD predictions provide a mechanistic understanding of the configuration-specific differences observed in vitro. Flow patterns in the ostium–sinus region, as well as the ventilation rate and driving pressure, show high sensitivities to AO location and orientation. At 1 m/s, the predicted AO-NO pressure drop ranges 2–18 mPa, with the lowest in AO-FC and highest in AO-B. Conclusions: The high sensitivity of sinus ventilation to AO configurations underscores the clinical importance of examining NO-adjacent openings in surgical planning and physiological interpretation. Full article

Methane is one of the most potent greenhouse gases, with a Global Warming Potential (GWP100) 27.9 times greater than that of CO₂ when measured as carbon dioxide equivalent. Therefore, the development and implementation of effective methods for reducing methane emissions are crucial for environmental protection, especially when these methods also provide additional technical or economic benefits. This article presents the results of an economic efficiency analysis conducted for a pilot-scale installation developed to reduce climate hazards in coal mines, based on a reactor for the catalytic oxidation of ventilation air methane. The economic feasibility of this installation operating under real conditions in underground coal mines was evaluated, and the analysis is based on actual operational data. The analysis was performed using a differential financial model. The capital and operating expenditures of the pilot-scale installation were compared with the costs of purchasing, installing, and operating a standard MK-500 cooling unit commonly used in Polish coal mines. The following economic efficiency indicators were obtained for the determined cash flows: Net Present Value (NPV) of 1.66 m EUR and Internal Rate of Return (IRR) of 24.6%. The results indicate that the pilot-scale technology becomes economically viable solely through the avoidance of methane emission penalties. The analysis identified the cost and macroeconomic parameters necessary for the economic viability of the technologies studied and established the methane emission penalty threshold at which operating the catalytic methane oxidation reactor system becomes justified (EUR 638/Mg CH₄). The paper presents the factors with the greatest and least impact on the economic efficiency of the analyzed pilot-scale installation. The proposed pilot-scale approach offers a realistic pathway for combining greenhouse gas mitigation with operational stability in underground mining. Full article

Numerical results are presented for a morphology fitted to a passive solar chimney attached to a room coupled with an earth-air heat exchanger. The effects of the variable thermophysical properties of air are included in the modelling. The considered operating mode is room cooling (summer ventilation) by means of an incoming airstream drawn from the soil at a temperature lower than that of the ambient. Buoyancy is assumed to be the only driving force acting on the fluid. A wide range of irradiance over the solar chimney walls, from 10 to 1000 W/m² (Rayleigh number based on the glazing wall from 1.77 × 10¹¹ to 1.77 × 10¹⁴), is analyzed. The impact of the incoming airstream temperature on the overall dynamic and thermal behavior of the system is studied. The induced mass-flow rate and average Nusselt number are presented as a function of relevant parameters for evaluating the passive device performance. The results reveal a strong influence of temperature and the position of the incoming cool airstream on room cooling. Some opposite effects on the relevant parameters are detected, but a sizeable increase in ventilation within the room for the middle and upper positions of the incoming duct is highlighted. Full article

Axial flow fans are widely used in high-speed train cooling and ventilation systems, where both static efficiency and noise reduction are critical performance requirements. In this study, the effects of hub geometry variation on the aerodynamic and acoustic characteristics of an axial flow fan are numerically investigated through three-dimensional simulations. Five fan configurations with different hub angles are analyzed under identical operating conditions. Steady aerodynamic performance is first evaluated using the Reynolds-averaged Navier–Stokes (RANS) approach with the k-ω shear stress transport (SST) turbulence model. The unsteady flow field is then resolved using large eddy simulation (LES) to capture the vortex structures and blade surface pressure fluctuations responsible for noise generation. The far-field aerodynamic noise is predicted based on the Ffowcs Williams–Hawkings (FW–H) acoustic analogy, and both tonal and broadband noise characteristics are analyzed using multiple virtual microphones. The results show that reducing the hub angle leads to improved aerodynamic performance at lower volumetric flow rates. Meanwhile, a reduction in tonal noise at the blade-passing frequency (BPF) and broadband noise at higher frequencies is observed. The findings demonstrate that appropriate hub angle design provides an effective approach for the simultaneous improvement of static efficiency and the reduction of aerodynamic noise of axial-flow fans used in high-speed train applications. Full article

The low-altitude atmospheric environment has been receiving increasing attention in recent years due to rising human activities and the emerging growth of the low-altitude economy. Urban wakes generate highly inhomogeneous, multiscale turbulent flows, posing challenges for momentum transport, pedestrian-level ventilation, and low-altitude aerial vehicle operations. Large eddy simulation of a neutral boundary layer over an idealized urban street canyon is conducted, and wavelet transforms combined with quadrant analysis are applied to investigate scale-dependent momentum transport across three wake zones: recirculation, entrainment, and detrainment. The results show that strong momentum transport across a broad range of scales is exhibited at the roof level of the recirculation zone. The momentum transport in the entrainment zone is governed by large-coherent-scale turbulence. On the contrary, the dynamics are governed by small-scale turbulence activities accompanied by distinct quadrant asymmetry in the detrainment zone because of the major energy contribution from Q2 and Q4 events. Furthermore, the multiscale characteristics of turbulent transport produce distinct frequency signatures across different wake zones, underscoring their dynamically heterogeneous nature and potential implications for UAV operation. Full article